Process for producing a three-dimensional object

ABSTRACT

A process is provided for producing a three-dimensional object having the steps forming the object ( 3 ) in a container ( 1, 200 ) arranged within a process chamber ( 100 ) on a carrier ( 4 ) which can be displaced in the container by sequential selective solidification of layers of a pulverulent material ( 11 ) which can be solidified by the action of electromagnetic or particle radiation at positions corresponding to the cross-section of the object in the particular layer, characterized by the step of controlled removal of non-solidified pulverulent material ( 11 ) after completing the object ( 3 ).

The present application is a divisional application of U.S. Ser. No.10/049,305, filed Feb. 6, 2002 (now U.S. Pat. No. 6,932,935), which is a371 of Application No. PCT/EP00/07318, filed Jul. 28, 2000.

The invention relates to a process for producing a three-dimensionalobject having the steps of forming an object in a container arrangedwithin a process chamber on a carrier which can be displaced in thecontainer by sequential selective solidification of layers of asolidifiable pulverulent material at positions corresponding to thecross-section of the object in the particular layer according to and adevice for producing a three-dimensional object by sequentialsolidification of layers of a solidifiable powder material having acontainer for accommodating the object to be produced, and a carrierwhich can be displaced in the container.

In a process, known for example from U.S. Pat. No. 4,863,538, forproducing a three-dimensional object by means of selective lasersintering, the object is produced by successive selective solidificationof layers of a pulverulent material at positions corresponding to theobject in the particular layer under the action of a laser beam. Theobjects thus produced are still hot immediately after they are completedand do not yet have their final solidity. Furthermore, the object mustbe freed of non-solidified powder before it may be used. Depending onapplication, it is also desirable or necessary to subsequently treat theobjects.

A process and a device is known from U.S. Pat. No. 5,846,370. There itis proposed to construct the object in a container which is providedwithin a process chamber and after completing the object may be removedfrom the latter and may be used as a cooling device. It is known fromEuropean Patent No. 0 632 761 to also solidify a container wallsurrounding the object together with the object and to place thiscontainer thus formed together with the object at a separate locationfor cooling after the building process. It is known from European PatentNo. 0 289 116 to produce an object by means of laser sintering of apowder, wherein the powder layers are applied by means of a fluidizedbed process. Heated or cooled gas is supplied in order to keep theobject at a uniform temperature during the building process. It is knownfrom European Patent No. 0 287 657 to pass a stream oftemperature-controlled air through the powder bed, in order to removeheat from the object during the building process.

It is also known from German utility model DE 29 506 716.6 to remove orto unpack an object produced by means of selective laser sinteringmanually from the non-solidified powder still surrounding the objectafter construction. It is known from WO 00/21673 to provide a changeablebuilding frame for the object in a laser sintering device which can beremoved quickly and simply from the laser sintering device andre-installed and hence facilitates rapid job change. A device and aprocess is known from U.S. Pat. No. 5,569,431, in which an object formedby means of stereolithography is automatically raised up from a bath ofliquid material which can be photo-solidified. Furthermore, European 0403 146 discloses a stereolithography device, in which a device in whichthe object is constructed and a subsequent treatment device areprovided. A transport device for transporting the object between the twois also provided.

It is the object of the invention to provide a process and a device forproducing a three-dimensional object from solidifiable powder material,with which the overall production process may be simplified, automatedand/or shortened and the precision during the production of the objectis improved.

The present invention provides a process for producing athree-dimensional object having the steps forming the object (3) in acontainer (1, 200) arranged within a process chamber (100) on a carrier(4) which can be displaced in the container by sequential selectivesolidification of layers of a solidifiable pulverulent material (11) atpositions corresponding to the cross-section of the object in theparticular layer, characterized by the step of controlled removal ofnon-solidified pulverulent material (11) after completing the object(3).

It also provides a process for producing a three-dimensional objecthaving the steps forming the object (3) in a container (1, 200; 300)arranged within a process chamber (100) on a carrier (4) which can bedisplaced in the container by sequential selective solidification oflayers of a solidifiable pulverulent material (11) at positionscorresponding to the cross-section of the object in the particularlayer, characterized by the step of controlled cooling of the object (3)after completing.

It further provides a process for producing a three-dimensional objecthaving the steps: forming the object (3) by sequential selectivesolidification of layers of a solidifiable pulverulent material (11) atpositions corresponding to the cross-section of the object in theparticular layer, characterized in that the object formed isautomatically subjected to infiltration.

The invention also provides a device for producing a three-dimensionalobject by sequential solidification of layers of a solidifiable powdermaterial having a container (1; 200) for accommodating the object (3) tobe produced, a carrier (4) which can be displaced in the container, anda device (50; 500) for controlled removal of non-solidified pulverulentmaterial (11) after completing the object (3).

Further, it provides a device for automatic unpacking and/or cooling ofa three-dimensional object, which is produced by sequentialsolidification of layers of a solidifiable powder material, having acontainer (1; 200) for accommodating the object (3) to be produced, acarrier (4) which can be displaced in the container and having a device(50; 500) for controlled removal of non-solidified pulverulent material(11) after completing the object (3) and/or having a device forcontrolled cooling of the object formed (500; 600).

Further features and advantages of the invention can be seen from thedescription of exemplary embodiments using the figures.

Of the figures

FIG. 1 shows a schematic sectional view of the device of the invention;

FIG. 2 shows a schematic sectional view of a detail of the deviceaccording to a first embodiment of the invention;

FIG. 3 shows a schematic sectional view of a detail of the deviceaccording to a second embodiment of the invention;

FIG. 4 shows a schematic sectional view of a detail of the deviceaccording to a further embodiment of the invention; and

FIG. 5 shows a schematic sectional view of a detail of the deviceaccording to a still further embodiment of the invention.

As can be seen in particular from FIG. 1, the device for producing athree-dimensional object has a container open at the top or buildingcontainer 1 having an upper rim 2. The cross-section of the container 1is greater than the largest cross-sectional surface area of an object 3to be produced. A carrier 4 for supporting the object to be formedhaving an essentially flat surface 5 facing the upper rim 2 is providedin the container 1. The carrier 4 can be moved up and down in thecontainer 1 in vertical direction by means of a drive indicatedschematically in FIG. 1. The upper rim 2 of the container 1 defines aworking plane 6.

The container 1 is releasably attached in a process chamber 100, so thatit can be removed from the process chamber 100 together with the object3 formed therein.

A radiation device in the form of a laser 7, which emits a directedlight beam 8, is arranged above the working plane 6. A deflecting device9 is provided, for example as a system of galvanometer mirrors, by meansof which the light beam 8 as deflected beam 8′ can be deflected to eachrequired position of the working plane 6.

A coater 10, for applying a layer of a powder material 11 to besolidified to the carrier surface 5 or a layer which is solidified inthe end, is provided. The coater 10 can be moved back and forth over theworking plane 6 by means of a schematically indicated drive from a firstend position on one side of the container 1 to a second end position onthe opposite side of the container 1.

A control device 40 is also provided, by means of which the drive to setthe position of the carrier 4, the drive for moving the coater 10 andthe drive for adjusting the deflecting device can be controlled incoordinated manner or independently of one another.

In a first embodiment of the invention shown in FIG. 2, the device forproducing the object has a device 50 preferably arranged outside theprocess chamber 100 for controlled removal of the complete object fromthe container 1. The device 50 has a mounting 51 shown onlyschematically, in which the container 1 can be inserted and is held,after it is removed from the process chamber. The device 50 also has adrive indicated schematically in FIG. 2 for upward and downward movementof the carrier in the device 50. The drive is designed such that thecarrier may be moved at an adjustable rate continuously or stepwiseagainst the upper rim 2 of the container. Furthermore, the drive isdesigned so that the carrier 4 may be lowered again after it has reachedits uppermost position.

A covering 52 sealing the container 1 from the surroundings at its openside is also provided in the form of a dome-like hood, which rests withits lower rim on the upper rim 2 of the container 1. The covering 52 canbe placed on the container and a seal is provided between the upper rim2 of the container 1 and the covering, by means of which seal a hermeticseal to the atmosphere is guaranteed. The covering has two openings 53and 54 opposite one another which are provided at a predetermineddistance from the lower rim of the covering 52. The openings 53, 54 arein each case connected to a supply pipe 55 or a removal pipe 56 forsupplying a compressed gas or for removing the gas and powder particlesfluidised by the gas stream. The supply pipe 55 is connected to a device57 for supplying a gaseous medium preferably with a compressed airsource 57. The removal pipe 56 is connected to a collection container 58for removed powder material. The openings 53 and 54 in the covering 52are arranged such that when the compressed air source 57 is connected, agas stream flowing essentially tangentially over the upper rim 2 of thecontainer is produced. The compressed air source 57 can be adjusted sothat the strength of the air stream can be controlled. Furthermore, thetemperature of the gaseous medium can be controlled so that atemperature required for cooling can be set.

In the process of the invention, the object is initially produced inknown manner on the carrier 4 within the container 1 in the processchamber 100. Hence, the carrier 4 is first moved to the highestposition, in which the carrier surface 5 lies at a distance of one layerthickness of the first layer to be applied below the upper rim 2 of thecontainer 1. The coater 10 is then moved over the working plane 6 and afirst layer of powder 11 to be solidified is applied. The deflectingdevice 9 is then controlled such that a region of the powder materialcorresponding to the cross-section of the object in this layer issolidified by the laser beam 8. The carrier 4 is then lowered and a newlayer applied and likewise again solidified. These steps are repeated sooften until the object 3 is completed. Plastic powder, such as forexample polyamide powder, metal powder, ceramic powder, plastic-coatedsand or combinations thereof, is used as powder material 11, dependingon the area of application.

The container is then removed from the process chamber 100 together withthe object 3 formed therein and introduced into the device 50 forunpacking the object 3. The carrier 4 is thus situated within thecontainer 1 in its lowest position. Powder material 11 which is not yetsolidified is situated between the object 3 formed and the containerwall. When using plastic powder, the object 3 is typically still hotimmediately after being completed and has not yet reached its finalsolidity. For gentle unpacking and cooling of the object, the covering52 is now placed on the container 1 and the compressed air source 57 isconnected. The carrier 4 is then moved upwards either continuously at anadjustable rate or stepwise within the container, so that a quantity ofnon-solidified powder is always situated above the container rim 2 andis held by the covering 52. The compressed air source 57 is adjusted sothat an adequately strong air stream passes essentially tangentiallyover the powder surface and thus entrains non-solidified powder, whichis removed through the outlet opening 53 and the removal pipe 56 and iscollected in the collection container 58. As soon as the object 3arrives within the region of the air stream passing over the surface byraising the carrier 4, it is cooled by the air stream. When the carrier4 is in its uppermost end position, the covering 52 is removed and theobject is taken out. It is thus adequately cooled. Hence, the object 3is removed from the container 1 in predetermined manner by adjusting thetemperature and the pressure of the air stream, and the moving rate ofthe carrier within the container in predetermined manner and thecontainer 1 is again free for new insertion in the process chamber 100.The process has the advantage that by controlled unpacking and coolingof the object 3, sudden cooling is avoided and at the same time thenon-solidified powder material is removed and cooled likewise slowly andin controlled manner, so that it has a high quality for re-use. On theother hand, the object 3 is only removed after this procedure, so thatit does not have to be touched in the hot and still soft state, and thusis not exposed to deforming forces. Furthermore, cooling and unpackingoutside the process chamber has the advantage that the latter is freefor forming new objects.

In an alternative embodiment, a suction pump, which assists transport ofthe non-solidified powder, is connected to the removal pipe 56. The airmay also be circulated, a connection pipe is then provided for thisbetween the air removal pipe 56 and the air supply pipe 55, in which afilter is arranged to separate fluidised powder and air. Instead of air,a further gas, for example a protective gas, such as nitrogen, may alsobe used to prevent the powder, for example from oxidising. The overalldevice 50 may also be arranged within the process chamber 100, whereinhowever, the process chamber is then occupied during unpacking andcooling.

In a modification of the embodiment according to FIG. 2, instead ofopenings 53, 54, more than two openings are provided in differentpositions. The gas stream may also be directed other than tangentiallyto the surface. Furthermore, a device is provided to control thedirection of the gas stream, for example in the form of a controllablenozzle.

In a further embodiment shown in FIG. 3 of an device for removing theobject from the building container, the container 200 is designed suchthat it has a frame 60 having preferably square or rectangularcross-section, within which the carrier 4 can be moved up and down. Anannular or collar-like attachment or rim 62 is provided, which can beplaced on the upper rim 61 of the container frame 60 and can be removedagain. The attachment 62 is designed such that it forms an overflowdevice, preferably in an outwardly curved overflow edge 63 or anoverflow rim rounded in the region of the overflow on at least one ofthe four sides of the container frame 60, and projects on the otherthree sides beyond the rim 61 of the container frame 60, so that itforms a device at the top for preventing powder or object from fallingout during movement of the carrier 4. The container 200 is held by itsframe 60 in a mounting 70, which is preferably arranged outside theprocess chamber 100. A tilting device 71 is also provided, with whichthe container 200, together with its mounting 70, can be tilted invertical direction about a predetermined and adjustable angle A, so thatthe displacement axis V of the carrier 4 in the container 1 is tilted bythis predetermined angle A with respect to the vertical.

A sieve device 80, preferably in the form of a shaking sieve, isarranged below the overflow edge 63 of the container 1 and a collectioncontainer 90 is arranged below the shaking sieve.

In a modification of the embodiment according to claim 3, the container1, the sieve device 80 and optionally the collection container 90 arearranged in a dust-tight and optionally gas-tight chamber in order toavoid dust and to facilitate the control of the temperature of thesurroundings.

In the process according to this embodiment, first of all the object 3is completed within the process chamber as described above. It is thusquite possible that several separate objects 3, 3′, 3″ are producedwithin the container, which are separated from one another bynon-solidified powder material 11.

The container 200 is then removed from the process chamber and placed inthe mounting 70 of the device 500 for unpacking. The container 200 istilted by means of the tilting device 71 such that the axis V of thecarrier 4 has a predetermined angle A to the vertical in the directionof the sieve or collection device 80. The carrier 4 is then raisedcontinuously or stepwise, so that non-solidified powder material 11 ispushed over the overflow edge 63 and then falls on the shaking sieve 80.The mesh width of the sieve 80 is selected such that non-solidifiedpowder may be sifted off and collected and transported away for re-usein the collection container 90. The object or objects formed are alsopushed over the overflow edge 3 by the pressure of the following powdermaterial pushed over the overflow edge 63 by the carrier 4 movingupwards and collected in the shaking sieve 80, from where they may thenbe removed after sifting off the non-solidified powder material. Thetilting angle A may be changed, for example increased, during raising ofthe carrier 4, so that the powder and the objects may be pushedcompletely from the container over the overflow edge 63. The container200 does not necessarily have to be tilted. Controlled unpacking, thatis the controlled removal of non-solidified powder material, is crucial.

In this embodiment, it is also possible to provide a cooling device, forexample in the form of an air or gas stream G passing along the powdersurface, as a result of which objects emerging on the powder surface andthe powder itself are cooled.

A combination of the embodiments shown in FIG. 2 and FIG. 3 for thedevice for unpacking are also possible. Overflow of the powder over theedge 63 may be assisted, for example by compressed air or by a vibratorprovided on the overflow edge, the container or the carrier.

In a further embodiment, a device is provided, with which thenon-solidified powder is removed mechanically in controlled manner. Sucha device may be formed, for example by one or more brushes, by means ofwhich non-solidified powder is conveyed away from the surface during theupward movement of the carrier in the container, and optionally powderresidues adhering to the object are removed. The mechanical device forremoving the powder may also be used for assisting powder removal duringsieving.

Moreover, the invention is not restricted to the use of a gas stream forremoving non-solidified powder material. It is also possible to use adifferent fluid medium instead of the gas stream, for example agas/powder mixture, a liquid or a liquid/powder mixture. By using asuitable fluid medium, it is possible to treat the surface of thecomponent at the same time as removing the powder, for example to bringabout smoothing by means of a gas/powder stream or hardening by means ofreactive gases. Such a subsequent treatment of the component may takeplace at the same time and automated with the removal of powder in thedevice for removing the object from the container or after powderremoval.

Both the embodiment according to FIG. 2, and that according to FIG. 3 orcombinations of the same may also have additionally a temperaturecontrol device for controlling the temperature of the fluid medium or ofthe gas stream and/or the surrounding atmosphere. In a step forcontrolling temperature for controlled cooling of the object formed, theambient temperature corresponds initially to the object temperature andis then slowly reduced during sieving.

In a further embodiment, which is shown in FIG. 4, the carrier surface5, also designated as building platform, on which the object isconstructed in a container 300, is designed to be porous, as shown inthe left-hand half of FIG. 4, or equipped with openings 500, as shown inthe right-hand half of FIG. 4. A gas, for example air, which produces atype of fluidised bed and which loosens the powder 11 surrounding theobject, is blown in from below through the porous building platform orthe openings. Compactions or lumps which possibly exist are thusloosened, which facilitates unpacking, The direction, flow, rate andtemperature of the gas can be controlled individually or in combinedmanner. Hence, the temperature of the whole powder bed, including theobject, may be controlled. This embodiment can be combined with theexemplary embodiments described hitherto for unpacking the object.Alternatively or additionally to blowing in through the carrier surface5, the gas may also be blown into the powder bed through the side wallsof the container 300 or from the top.

FIG. 5 shows a device for controlled cooling of the object as a furtherembodiment of the invention. One or more supply devices 600 for gas inthe form of probes or similar are passed through the building platform 5and/or the side walls and/or the upper powder surface of the container300, wherein the position known from CAD data and geometry of theparticular object 3 is taken into account. Gas is passed at controlledtemperature through the supply devices 600, so that the object may becooled by local specific convection under defined temperatureconditions. The gas also loosens the powder bed, as a result of whichunpacking is facilitated.

Depending on the powder material used, the building process may becarried out, so that the object is not hot immediately after completingand therefore does not require cooling. Here too, the processes anddevices described have the advantage that the object is unpacked gentlyand without manual work. If the object already has adequate solidityimmediately after completing, instead of the continuous or stepwiseraising of the carrier, the whole content of the container may beemptied straight onto the sieve or collection device, for example byopening the container. This alternative has the advantage that theentire process is accelerated, wherein the process and means describedabove for powder removal and cooling may likewise be used.

It is crucial that means for controlled removal of the non-solidifiedpowder material are provided, which faciliate automatic unpacking of theobject formed from the container in controlled manner without manualwork.

A further embodiment of the invention consists in specificallyinfluencing the object properties by controlled unpacking and/or coolingby means of a gas or a fluid medium, which renders manual subsequenttreatment superfluous. Chemical subsequent treatment of the surface ofthe object formed may for example take place with the blowing-in of gas.Hence, the conventional production steps between production and use ofthe object can be accelerated. According to a further embodiment of theinvention, the object, after non-solidified powder has been removed, isautomatically subsequently treated, for example subjected toinfiltration using wax or epoxy resin. The temperature of the buildingchamber is thus set to a suitable value necessary for infiltration viathe temperature control.

The invention is also not restricted to the fact that a laser beam isused for solidifying the powder material. Instead of using a laser beam,the powder may also be solidified in a different manner, for exampleusing other energy beams, such as for example using an electron beam orby selective adhesion, for example using binder or adhesive selectivelyinjected from a printer head.

1. A process for producing a three-dimensional object, the processcomprising the steps of: providing a container arranged within a processchamber and a carrier that can be moved in the container; forming theobject on the carrier in the container by sequential selectivesolidification of layers of a solidifiable powder material at positionscorresponding to the cross-section of the object in the particularlayer; cooling the object during removing of the non-solidified powdermaterial, wherein the cooling is performed in a controlled manner; andraising the carrier during cooling.
 2. The process according to claim 1,wherein the removing of non-solidified powder material is performed by afluid stream.
 3. The process according to claim 1, wherein the coolingis effected by providing a fluid to the object.
 4. The process accordingto claim 3, wherein providing the fluid comprises blowing the fluid intothe non-solidified powder.
 5. The process according to claim 3, whereinproviding the fluid comprises blowing the fluid over an exposed surfaceof the object in the powder.
 6. The process according to claim 3,wherein providing the fluid comprises directing the fluid streamessentially tangentially to the powder surface to cool the object. 7.The process according to claim 1, further comprising providingadditional treatment to the object during cooling, said additionaltreatment including one of chemical, physical or mechanical treatment ofthe surface of the object.
 8. The process according to claim 3, whereinthe fluid is a gas or a liquid.